In: Statistics and Probability
=
Solution :
Given that ,
mean = 
 = 355
standard deviation = 
 = 80
n = 48

= 355

=
  /
n= 80 / 
48=11.55
P(340< 
   <360 ) = P[(340-355) /11.55 < (
-
) / 
 < (360-355) /11.5 )]
= P(-1.30< Z <0.43 )
= P(Z <0.43 ) - P(Z <-1.30 )
Using z table
=0.6664-0.0968
=0.5696
probability= 0.5696